The present invention pertains to a method of creating an image on a recording medium with an ink composition that is solid at room temperature and liquid at elevated temperature. The present invention also pertains to a system for creating an image on a recording medium with said ink composition.
A method of creating an image on a recording medium with an ink composition that is solid at room temperature and liquid at elevated temperature (also called “hot melt” or “phase change ink”) is known from U.S. Pat. No. 6,497,940. This patent describes a recording medium for the ink composition which has improved clarity, improved resistance to surface scratching and improved ink adhesion. The recording medium comprises a polyethylene terephthalate support coated with a lower receptor layer comprising 82-97 wt. % of silica and 3-18 wt. % of PVA, polyvinylpyrrolidone, polyacrylamide, methylcellulose or gelatin. An optional upper layer comprises 32-70 wt. % of a matrix polymer, 15-52 wt. % of inorganic particulate material and 5-53 wt. % of soft polymer mixture. The term ‘soft polymer mixture’ describes a polymer or mixture of polymers that soften during the image transfer step of the printing. The softening allows the ink composition and the upper layer to become chemically or physically mated for mechanical durability reasons. The soft polymer matrix must be sufficiently soft to allow the ink composition and the coating to become intimately interrelated and yet rigid enough to avoid scratching and sticking with adjoining films.
Although suitable to obtain adequate mechanical durability, a disadvantage of this known method is that the print quality deteriorates when the printed medium is subjected to thermal load, for example by storing the printed medium at 35° C. for several weeks or months. It is, for example, noticed that the gloss level decreases substantially, and that local artefacts arise in the printed images.